Implementation of PFR in BLDC Motor Using …ijire.org/gallery/37-march-515.pdfbe used for...

Implementation of PFR in BLDC Motor Using Landsman Converter

1 Mr. GANESAN.M, 2 VENGAMA TANYA SREE, 2 SANDHYA.S, 3 TAMIL OVIYAM.M

1 Assistant Professor, Department of Electrical and Electronics, R.M.K. Engineering College, Thiruvallur, Chennai. 2,3,Department of Electrical and Electronics Engineering, R.M.K. Engineering College, Thiruvallur, Chennai.

Abstract-- This article configures about power factor regulation in Brushless DC motor (BLDCM) using Landsman

converter. The speed control of the drive is achieved through adjusting DC bus voltage of voltage source inverter (VSI). In

BLDCM low frequency switching signal are used for electronic commutation which reduces the switching power losses of

six solid state switches of VSI. This Landsman Converter-based power factor regulator operating in discontinuous inductor

current mode is used to control DC bus voltage and desired PFR is achieved. For evaluating the performance of the proposed

drives a prototype is developed. The BLDC performance is evaluated using varying the AC main voltage.

Keywords: BLDC motor, Landsman converter, Power factor regulation, Three-phase full Bridge Inverter.

I. INTRODUCTION

After Among many electrical motors, Brushless DC motor is very efficient low power appliances. It is suitable for many

applications because of its ruggedness, high torque, high efficiency, low electromagnetic interference problems. Various

applications including industrial tools, heating ventilation and air conditioning, medical equipment, and robotics use this

type of motor for better outcome. To achieve power factor, close to unity at AC supply PFR converters are used. PFC

converter driven BLDC motor drives are used. Primarily used converters are PFC-based Cuk, single ended primary

inductance converter, Zeta converter are used in the PFR regulation. In proposed system Landsman converter is used for

the same purpose. In a brushless DC motor stator is made up of three-phase intense windings and rotor has permanent

magnets. With the presence of Hall-effect positioning sensor a three leg voltage source inverter (VSI) is used for electronic

commutation of BLDCM. Hence, major problems with brushes and commutator are eliminated. A typical BLDCM drive

usually consists of a diode bridge rectifier (DBR) with DC bus capacitor followed by a VSI. The six solid-state switches of

VSI is driven by three-phase pulse-width modulation (PWM) signals which feeds the BLDCM. With AC supply to achieve

power factor close to unity PF regulation (PFR) converters are embedded followed by a DBR. It acts as a significant factor

as it affects the rating of passive elements of converter. PFC converter based on boost configuration has emerged as popular

configuration for driving a brushless DC motor. In such schemes a constant DC-Link voltage is maintained at DC bus

capacitor of VSI

II. EXISTING SYSTEM

The PFC converter driven BLDC motor drives have been used for various applications. PFC converter is based on boost

configuration. This configuration has been widely used for driving a BLDCM. In such cases, a constant DC-link voltage is

maintained at DC bus capacitor of VSI. Similarly for controlling speed, high-frequency signals are used. The BLDCM drive

requires a large amount of sensing due to higher switching losses. In case of a DC voltage control low frequency signals can

be used for electronic commutation of motor.PFC-based Cuk, single ended primary inductance converter (SEPIC), Zeta

and Luo converters using variable voltage control fed BLDCM drive have been proposed. An isolated configuration of

PFC-Zeta converter fed drive for BLDCM, bridgeless configurations of PFC based Cuk and CSC has been also proposed.

These configurations have lower conduction losses in the front end PFC converter due to partial elimination of DBR, except

at the expense of high amount of passive components.

INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH EXPLORER

VOLUME 5, ISSUE 3, MAR/2018

ISSN NO: 2347-6060

http://ijire.org/269

Combining the advantages of the isolated and bridgeless PFC converter, a bridgeless-isolated PFC converter has also been

proposed. A Landsman converter as a modification of a CSC converter for limiting the current ripples in the output side

capacitor has been proposed. In CSC converter, due to the operation of an inductor in discontinuous conduction, the input

and output currents have higher current ripple which is a major drawback of this CSC converter. Interestingly, the addition

of a small inductance at the output of this conversion stage yields a true switched-mode topology. These yield to low-output

ripple current in the DC link. In the existing system the converters used are not as efficient as Landsman converter. So the

proposed system uses the Landsman converter to increase the efficiency of the brushless DC motor to increase the power

factor close to unity.

III. PROPOSED SYSTEM

A. BLOCK DIAGRAM REPRESENTATION

A Landsman converter is a modification of canonical switching cell(CSC) converter This converter is proposed for limiting

output current ripple. As the inductor in CSC converter operates in discontinuous conduction, the current ripple is high in

input and output currents. But an addition of a small inductance at the output of this conversion stage yields low output

ripple current. A landsman converter working in a discontinuous inductor current mode acts as an inbuilt power factor pre-

regulator for attaining power factor close to unity at AC mains. Variable DC-link voltage of VSI is applied for controlling

the speed of the motor. This allows low-frequency switching operation for VSI switches, by electronic commutation of

BLDCM, to reduce switching losses in six insulated gate bipolar transistors of VSI.The parameters of landsman converters

are designed and selected to operate in a discontinuous inductor current mode for obtaining a high power factor at a wide

range of speed control. Landsman converter-based PFR is designed to operate in DICM for PF regulation. The current in

input inductor (Li) becomes discontinuous during switching period (Ts) in DICM operation. The three operating stages of a

PFR Landsman converter are

FIG 1 BLOCK DIAGRAM



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B. HARDWARE DESCRIPTION

The hardware components of the system are

1. Three phase full bridge inverter

2. Brushless DC electric motor

3. PID controller

4. Landsman converter

5. Simulation

1) THREE PHASE FULL BRIDGE INVERTER

The 3-phase bridge type VSI with square wave pole voltages has been considered. The output from this inverter is to be fed

to a 3-phase balanced load. The diagram shows the power circuit of the three-phase inverter. This circuit may be identified

as three single- phase half-bridge inverter circuits put across the same dc bus. The individual pole voltages of the 3-phase

bridge circuit are identical to the square pole voltages output by single-phase half bridge or full bridge circuits. The three

pole voltages of the 3-phase square wave inverter are shifted in time by one third of the output time period. These pole

voltages along with some other relevant waveforms have been plotted in diagram The horizontal axis of the waveforms in

diagram has been represented in terms of ‘ωt’, where ‘ω’ is the angular frequency (in radians per second) of the fundamental

component of square pole voltage and ‘t’ stands for time in second. In diagram the phase sequence of the pole voltages is

taken as VAO, VBO and VCO. The numbering of the switches in diagram has some special significance vis-à-vis the output

phase sequence.

FIG 2 THREE PHASE BRIDGE INVERTER

The basic 3-phase inverter is a six-step inverter. A step is defined as a change in the firing sequence. A 3-phase thyristor

bridge-inverter is shown in Fig. 11.49. Th1 to Th6 are the six load-carrying thyristors while D1 to D6 are the free-wheeling

diodes. Each pair of thyristors in a branch (Thl and Th4; Th2 and Th5; Th3 and Th6) are gated for T/2 and are out-of-phase

with each other, i.e. they are never gated simultaneously. Th1, Th2 and Th3 are ired out-of-phase progressively by 120° and so

are Th4, Th5 and Th6. This is a must to obtain three output voltages out-of-phase 120°.



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FIG 3 SEQUENCE OF CONDUCTING THYRISTORS IN THREE-PHASE BRIDGE INVERTER AND OUTPUT

VOLTAGE WAVEFORMS

shows the conducting periods of various thyristors as per the firing sequence indicated above. Over an angle of 2π, six

periods (one-sixth of each cycle period) are recognized and the thyristors conducting in these periods are identified. It is

noticed that in any one period only three thyristors are conducting. The frequency of firing is six times the output frequency.

The circuit models during three typical consecutive periods corresponding to the positive half-cycle of VAN are drawn in

diagram and the output voltages in terms of the input dc voltage (Vdc) are determined. The voltage waveforms for three

phase-to-neutral voltages of the 3-phase inverter can be easily drawn by this procedure. It is immediately obvious that these

voltages are out-of-phase by 120°. The phase sequence can be reversed by simply reversing the sequence of firing the

thyristors. The line-to-line voltages are found by taking the difference of phase voltages. The waveform of VAB=VAN-VBN is

illustrated. It is also easily seen that the fundamental components of line-to-line (or phase-to-neutral) voltages form a

balanced set. The free-wheeling diodes permit currents to flow which are out-of-phase with these voltages.



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2)BRUSHLESS DC ELECTRIC MOTOR

Brushless DC electric motor (BLDC motors, BL motors) also known as electronically commutated motors (ECMs, EC

motors), or synchronous DC motors, are synchronous motors powered by DC electricity via an inverter or switching power

supply which produces an AC electric current to drive each phase of the motor via a closed loop controller. The controller

provides pulses of current to the motor windings that control the speed and torque of the motor. The construction of a

brushless motor system is typically similar to a permanent magnet synchronous motor (PMSM), but can also be a switched

reluctance motor, or an induction (asynchronous) motor. The advantages of a brushless motor over brushed motors are

high power to weight ratio, high speed, and electronic control. Brushless motors find applications in such places as computer

peripherals (disk drives, printers), hand-held power tools, and vehicles ranging from model aircraft to automobiles. Because

the controller implements the traditional brushes' functionality it needs the rotor's orientation/position (relative to

the stator coils). This is automatic in a brushed motor due to the fixed geometry of rotor shaft and brushes. Some designs

use Hall effect sensors or a rotary encoder to directly measure the rotor's position. Others measure the back-EMF in the

undriven coils to infer the rotor position, eliminating the need for separate Hall effect sensors, and therefore are often

called sensor less controllers. A typical controller contains 3 bi-directional outputs (i.e., frequency controlled three phase

output), which are controlled by a logic circuit. Simple controllers employ comparators to determine when the output phase

should be advanced, while more advanced controllers employ a microcontroller to manage acceleration, control speed and

fine-tune efficiency. Controllers that sense rotor position based on back-EMF have extra challenges in initiating motion

because no back-EMF is produced when the rotor is stationary. This is usually accomplished by beginning rotation from an

arbitrary phase, and then skipping to the correct phase if it is found to be wrong. This can cause the motor to run briefly

backwards, adding even more complexity to the startup sequence. Other sensor less controllers are capable of measuring

winding saturation caused by the position of the magnets to infer the rotor position. Two key performance parameters of

brushless DC motors are the motor constants KT (torque constant) and Ke (back-EMF constant also known as speed

constant KV = 1/Ke ).

FIG 4 THREE PHASE BRUSHLESS DC MOTOR



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3)PID CONTROLLER

a) Working of PID Controller

With the use of low cost simple ON-OFF controller only two control states are possible, like fully ON or fully OFF. It is

used for limited control application where these two control states are enough for control objective. However, oscillating

nature of this control limits its usage and hence it is being replaced by PID controllers.PID controller maintains the output

such that there is zero error between process variable and set point/ desired output by closed loop operations. PID uses

three basic control behaviors that are explained below.

b) P- Controller:

FIG 5 P-CONTROLLER

Proportional or P- controller gives output which is proportional to current error e (t). It compares desired or set point with

actual value or feedback process value. The resulting error is multiplied with proportional constant to get the output. If the

error value is zero, then this controller output is zero.

FIG 6 P-CONTROLLER RESPONSE

This controller requires biasing or manual reset when used alone. This is because it never reaches the steady state condition.

It provides stable operation but always maintains the steady state error. Speed of the response is increased when the

proportional constant Kc increases.

c) I-Controller:

FIG 7 PI-CONTROLLER

Due to limitation of p-controller where there always exists an offset between the process variable and set point, I-controller

is needed, which provides necessary action to eliminate the steady state error. It integrates the error over a period of time

until error value reaches to zero. It holds the value to final control device at which error becomes zero. Integral control

decreases its output when negative error takes place. It limits the speed of response and affects stability of the system. Speed

of the response is increased by decreasing integral gain Ki.



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FIG 8 PI-CONTROLLER RESPONSE

In above figure, as the gain of the I-controller decreases, steady state error also goes on decreasing. For most of the cases,

PI controller is used particularly where high speed response is not required. While using the PI controller, I-controller output

is limited to somewhat range to overcome the integral wind up conditions where integral output goes on increasing even at

zero error state, due to nonlinearities in the plant.

d) D-Controller:

FIG 9 PID CONTROLLER

I-controller doesn’t have the capability to predict the future behavior of error. So it reacts normally once the set point is

changed. D-controller overcomes this problem by anticipating future behavior of the error. Its output depends on rate of

change of error with respect to time, multiplied by derivative constant. It gives the kick start for the output thereby increasing

system response.

FIG 10 PID CONTROLLER RESPONSE

In the above figure response of D controller is more, compared to PI controller and also settling time of output is decreased.

It improves the stability of system by compensating phase lag caused by I-controller. Increasing the derivative gain increases

speed of response. So finally we observed that by combining these three controllers, we can get the desired response for the

system. Different manufactures designs different PID algorithms. Tuning methods of PID Controller Before the working

of PID controller takes place, it must be tuned to suit with dynamics of the process to be controlled. Designers give the

default values for P, I and D terms and these values couldn’t give the desired performance and sometimes leads to instability

and slow control performances. Different types of tuning methods are developed to tune the PID controllers and require

much attention from the operator to select best values of proportional, integral and derivative gains. Some of these are given

below.



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Trial and Error Method: It is a simple method of PID controller tuning. While system or controller is working, we can

tune the controller. In this method, first we have to set Ki and Kd values to zero and increase proportional term (Kp) until

system reaches to oscillating behavior. Once it is oscillating, adjust Ki (Integral term) so that oscillations stops and finally

adjust D to get fast response.

Process reaction curve technique: It is an open loop tuning technique. It produces response when a step input is applied

to the system. Initially, we have to apply some control output to the system manually and have to record response curve.

After that we need to calculate slope, dead time, rise time of the curve and finally substitute these values in P, I and D

equations to get the gain values of PID terms.

FIG 11 PROCESS REACTION CURVE

Zeigler-Nichols method: Zeigler-Nichols proposed closed loop methods for tuning the PID controller. Those are

continuous cycling method and damped oscillation method. Procedures for both methods are same but oscillation behavior

is different. In this, first we have to set the p-controller constant, Kp to a particular value while Ki and Kd values are zero.

Proportional gain is increased till system oscillates at constant amplitude. Gain at which system produces constant oscillations

is called ultimate gain (Ku) and period of oscillations is called ultimate period (Pc). Once it is reached, we can enter the

values of P, I and D in PID controller by Zeigler-Nichols table depends on the controller used like P, PI or PID, as shown

below.

ZEIGLER-NICHOLAS TABLE

e) PID CONTROLLER STRUCTURE

PID controller consists of three terms, namely proportional, integral and derivative control. The combined operation of

these three controllers gives control strategy for process control. PID controller manipulates the process variables like

pressure, speed, temperature, flow, etc. Some of the applications use PID controllers in cascade networks where two or

more PID’s are used to achieve control. Above figure shows structure of PID controller. It consists of a PID block which

gives its output to process block. Process/plant consists of final control devices like actuators, control valves and other

control devices to control various processes of industry/plant.

Feedback signal from the process plant is compared with a set point or reference signal u(t) and corresponding error signal

e(t) is fed to the PID algorithm. According to the proportional, integral and derivative control calculations in algorithm, the

controller produces combined response or controlled output which is applied to plant control devices. All control

applications don’t need all the three control elements. Combinations like PI and PD controls are very often used in practical

applications.



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FIG 12 PID CONTROLLER STRUCTURE

3)LANDSMAN CONVERTER

FIG 13 LANDSMAN FED BLDC MOTOR

Mode I: When switch (Sw) is on, an energy from the supply and stored energy in the intermediate capacitor (C1) are

transferred to input inductor (Li). The output inductor (Lo) starts discharging and the voltage of intermediate capacitor (vC1

) starts reducing while DC-link voltage (Vdc) starts increasing. The value of intermediate capacitor is large enough to store

required energy such that the voltage across the capacitor does not become discontinuous.

Mode II: In this mode of converter operation, switch is turned-off. An intermediate capacitor (C1) and DC-link side inductor

(Lo) are charging through the supply current while output inductor (Li) starts discharging. Hence, vC1 starts increasing in this

mode. Moreover, the voltage across the DC capacitor (Vdc) decreases.

Mode III: This is the DCM for converter operation as the input inductor (Li) is discharged completely and current iLi becomes

zero. The current of DC bus side inductor (iL ) starts increasing and the voltage of intermediary capacitor (vCo ) continues

to decrease in this mode.

5) SIMULATION



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You can use Simulink® to model a system and then simulate the dynamic behavior of that system. The basic techniques

you use to create the simple model in this tutorial are the same techniques that you use for more complex models.

To create this simple model, you need four Simulink blocks. Blocks are the model elements that define the mathematics of

a system and provide input signals:

Sine Wave — Generate an input signal for the model.

Integrator — Process the input signal.

Bus Creator — Combine multiple signals into one signal.

Scope — Visualize and compare the input signal with the output signal.

You can interactively start, stop, and pause individual simulations from the Simulink® Editor. You can view your

simulation results live and interact with the simulation in various ways, including changing tunable parameters. You can

also step forward or back through a simulation, and perform iterative simulations without recompiling your model.

With programmatic simulation, you can run and control simulations from the MATLAB® command prompt. You can also

programmatically enable simulation timeouts, capture simulation errors, and access simulation metadata.

Using the multiple simulations API, you can provide a collection of inputs to a model and run multiple simulations with

these inputs. With the parsim function, you can run multiple simulations in parallel. This is useful in situations such as

model testing, design of experiments, Monte Carlo analysis, and model optimization.

IV. CONCLUSION

A PFR-based Landsman converter fed BLDCM drive has been proposed for the use in low power household appliances.

Adjustable voltage control of DC bus of VSI has been used to control the speed of BLDCM which eventually has given the

freedom to operate the VSI in low frequency switching operation. A prototype of Landsman-based BLDCM drive has been

implemented with acceptable test results for its operation over complete speed range and its operation over universal AC

mains. Thus getting power factor close to unity.

V. ACKNOWLEDGEMENT

We would like to thank Mr.M.Ganesan,Assistant Professor , for helping us with the ideas for this paper.

REFERENCE

1. Singh, B., Singh, S.: ‘Single-phase power factor controller topologies for permanent magnet brushless DC motor drives’, IET Power Electron.,

2010, 3,(2), pp. 147–175

2. Singh, S., Bist, V., Singh, B., et al.: ‘Power factor correction in switched mode power supply for computers using canonical switching cell

converter’, IETPower Electron., 2015, 8, pp. 234–244



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3. Singh, B., Singh, S., Chandra, A., et al.: ‘Comprehensive study of single-phase AC-DC power factor corrected converters with high-frequency

isolation’, IEEE Trans. Ind. Inf., 2011, 7, (4), pp. 540–556

4. Gieras, J.F., Wing, M.: ‘Permanent magnet motor technology-design and application’ (Marcel Dekker Inc., New York, 2011)

5. Xia, C.L.: ‘Permanent magnet brushless DC motor drives and controls’ (Wiley Press, Beijing, 2012)

6. Zhu, Z.Q., Howe, D.: ‘Electrical machines and drives for electric, hybrid, and fuel cell vehicles’, IEEE Proc., 2007, 95, (4), pp. 746–765

7. Kim, K.T., Kwom, J.M., Lee, H.M., et al.: ‘Single-stage high-power factor half-bridge fly back converter with synchronous rectifier’, IET Power

Electron.,2014, 7, pp. 1–10

8. Bist, V., Singh, B.: ‘A unity power factor bridgeless Isolated-Cuk converter fed brushless-DC motor drive’, IEEE Trans. Ind. Electron.,

2014

9. Landsman, E.E.: ‘A unifying derivation of switching DC-DC converter topologies’.Proc. of PESC ’79 Record, San Diego, Calif., 18–22

June 1979, pp. 239–243

10. https://www.google.co.in/search?q=reference+books+for+bldc+otor&oq=reference+books+for+bldc++otor&aqs=chrome..69i57.10808j0

j7&sourceid=chrome&ie=UTF-8#



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